These experiments use ultrafast laser spectroscopy to study reaction and photodissociation dynamics in solution, probing both photodissociation and intramolecular energy transfer. They have observed the photodissociation dynamics of methylhypochlorite (CH3OCl) in different solvents by monitoring the disappearance of the Cl atom and have compared the flow of energy in vibrationally excited methyl iodide (CH3l) in solution and in the gas phase. This second experiment is one of the few direct comparisons of intramolecular vibrational energy flow in a solvated molecule with that in the same molecule isolated in a gas. Because of the importance of vibrational relaxation of molecules after photoisomerization, the other goal has been to probe the vibrational energy flow in both cis and trans-stilbene, a prototypical molecule for cis-trans isomerization.

Combining the techniques of direct excitation of overtone vibrations and time resolved spectroscopic detection permits detailed measurements of the vibrational and rotational relaxation of highly vibrationally excited molecules. Using this technique, we have measured vibrational and rotational relaxation in HF(v=3,4,5,). By observing near-infrared fluorescence, we determine the self-relaxation probabilities for HF(v=3,4,5) to be 0.19, 0.47, and 0.97, respectively, and find that the rates decrease more rapidly with temperature in these high levels than for v=1. Using laser double resonance to probe individual rotational states, we find phenomenological rotational relaxation rate constants which decrease montonically with rotational energy change in the vibrationally excited molecule. (Author).

The transfer of energy in isolated or colliding molecules is a fundamental process with practical consequences for complex phenomena occurring in atmospheric chemistry, combustion, molecular lasers, plasmas, and a host of other environments containing energetic species. We have developed a technique that combines vibrational overtone excitation, to prepare highly vibrationally excited initial states, and time-resolved spectroscopic detection, to probe the evolution of the prepared state, for studying energy transfer in vibrationally energized molecules. We have used this approach to determine directly, for the first time, the frequencies of the three ungerade vibrations in the first electronically excited state of acetylene. Using this information we have characterized highly vibrationally excited states of acetylene and directly the frequencies and rotational constants of the perturbing vibrational states at these energies. Combining these spectroscopic insights on the vibrationally and electronically excited states of acetylene has allowed us to determine the energy transfer rates and pathways in the collisional relaxation of a polyatomic molecule containing 10,000 cm-1 of vibrational energy, Rotational energy transfer is very rapid, occurring on about every other collision, but is essentially unaffected by the identity of the vibrational state in which the rotational relaxation occurs.

Charge and Energy Transfer Dynamics in Molecular Systems Comprehensive resource offering knowledge on charge and energy transfer dynamics in molecular systems and nanostructures Charge and Energy Transfer Dynamics in Molecular Systems provides a unified description of different charge and energy transfer phenomena in molecular systems with emphasis on the theory, bridging the regimes of coherent and dissipative dynamics and thus presenting classic rate theories as well as modern treatments of ultrafast phenomena. Starting from microscopic models, the common features of the different transfer processes are highlighted, along with applications ranging from vibrational energy flow in large polyatomic molecules, the motion of protons in solution, up to the concerted dynamics of electronic and nuclear degrees of freedom in molecules and molecular aggregates. The newly revised and updated Fourth Edition contains a more detailed coverage of recent developments in density matrix theory, mixed quantum-classical methods for dynamics simulations, and a substantially expanded treatment of time-resolved spectroscopy. The book is written in an easy-to-follow style, including detailed mathematical derivations, thus making even complex concepts understandable and applicable. Charge and Energy Transfer Dynamics in Molecular Systems includes information on: Electronic and vibrational molecular states, covering molecular Schrödinger equation, Born—Oppenheimer separation and approximation, Hartree-Fock equations and other electronic structure methods Dynamics of isolated and open quantum systems, covering multidimensional wave packet dynamics, and different variants of density operator equations Interaction of molecular systems with radiation fields, covering linear and nonlinear optical response using the correlation function approach Intramolecular electronic transitions, covering optical transition and internal conversion processes Transfer processes of electrons, protons, and electronic excitation energy Providing in-depth coverage of the subject, Charge and Energy Transfer Dynamics in Molecular Systems is an essential resource for anyone working on timely problems of energy and charge transfer in physics, chemistry and biophysics as well as for all engaged in nanoscience and organic electronics.

Excited States, Volume 7 is a collection of papers that discusses the excited states of molecules. The first paper reviews the rotational involvement in intra-molecular in vibrational redistribution. This paper analyzes the vibrational Hamiltonian as to its efficacy in detecting the manifestations of intra-molecular state-mixing in time-resolved and time-averaged spectroscopic measurements. The next paper examines the temporal behavior of intra-molecular vibration-rotation energy transfer (IVRET) and the effects of IVRET on collision, reaction, and the decomposition processes. This paper also describes how IVRET can decrease the anisotropy of the angular distribution of photo dissociating molecules that takes longer than the rotational period of disassociation. The third paper explains rotations and electronic decay by focusing on nonresonant light scattering, which is explained in the theory of radiationless transitions, when the exciting light source is included. The last paper shows how sub-Doppler techniques adapted from atomic physics can measure accurately dense rotational triplet structure and singlet-triplet couplings in high vibrational triplet levels. This book will prove helpful for researchers whose work involves physical chemistry or molecular chemistry and physicists involved in atomic or solid-state physics.